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Application migration strategies are driven by business requirements for cost optimization, agility, scalability, or could be to simply update old and outdated systems. There could be multiple migration scenarios where an application is getting migrated from on premise to cloud, migration from public cloud to private cloud environment, on premises server to public cloud environment, migrating application from one cloud provider to another cloud provider and so on.
6R’S Model: AWS Migration
In today’s topic we will look at 6 R’s model of AWS migration, which migration strategy to choose from based on requirements and its pros and cons.
Six R’s strategy is an adopted model from Gartner 5 R’s model published in the year 2010 and extended to 6 R’s. 6 R’s:
- Re-host,
- Re-platform,
- Re-factor/Re-architect,
- Re-purchase,
- Retire and
- Retain.
Retire
Post discovery of application you can decide if application is not required in future, then you just ‘retire’ or ‘sunset’ them and get rid of them as the organization is no longer going to use it.
Pros and Cons of Retire
Pros:
Elimination of the cost of application infrastructure and license costs if any and there are no migration costs.
Cons:
There is no downside as we are simply shutting down something which is no longer required.
Retain
Organization decides to keep application AS-IS before a re-evaluation sometime in near future. This kind of strategy might be applied in case of unsupported OS and applications or legacy applications that do not have a business justification for migration to cloud infrastructure.
Pros and Cons of Retain
Pros:
No migration cost and no work involved.
Cons:
There is no scope in area for technical improvement or optimization of cost.
Re-host
One of the most basic and popular ways to migrate to AWS cloud by simply re-hosting is also referred to as “Lift and Shift”. Which means take your applications or systems and move them exactly with similar configurations onto AWS cloud. Majority of applications this is followed as it is easy to re-architect/optimize them once they are running on AWS cloud. One common example to use this strategy is moving MS-SQL databases to an AWS EC2 instance.
Pros and Cons of Re-hosting
Pros:
- Quicker migrations
- Risk is minimized
- Automated and assisted by tools as this is natively supported by AWS and third-party tools
- Migration of whole system including VMs and databases
Cons:
- Potentially inherited performance issues and other problems
- If you are not using AWS migration tools and instead use some other third-party tools you may not get the advantages such as managed databases, Amazon RDS, DynamoDB, Aurora, Amazon RedShift etc.
Re-platform
Re-platform is also referred to as ‘Lift and reshape’ because here you can take advantage of AWS cloud capabilities. This kind of application strategy example could be taking MS-SQL database and deploy it on Amazon RDS MySQL and migrate your application to fully managed platform AWS Elastic Beanstalk.
Pros and Cons of Re-platform
Pros:
- Very less code change as option to use services which are closure to existing infrastructure
- No dependency on OS, hypervisor or underlying physical infrastructure
- Utilization of modern OS/DB features and functionalities
- Possibility to use automated tools in some cases
Cons:
- Additional planning is required and coordination efforts will be time consuming and highly priced
- Mandatory to have knowledge of new cloud services
Re-architect
One of the most advanced options wherein redesign of application is required in cloud native manner. So basically you are creating a serverless version of a legacy application. One possible scenario for this kind of cloud migration strategy could be migration of on premises Oracle database to Amazon Aurora PostgreSQL and choose to modernize monolithic application by fragmenting it into small microservices and leverage services like Amazon Elastic Kubernetes service, AWS Lambda or AWS Fargate.
Pros and Cons of Re-architect
Pros:
- Improved efficiency, scalability, and costs
- Elimination of dependency on custom hardware and proprietary technology platform
- No need to maintain underlying physical infrastructure (Servers)
Cons:
- Require thorough and careful evaluation of vendors and partners
- More time and effort required to re-architect
- Require in-depth understanding of all aspects of application, compliance, code, design etc.
Re-Purchase
This involves abandoning existing software or application and migrating to cloud application. This cloud migration can be of two forms – transfer software license from on premises server to AWS or complete replacement of current application with SaaS choice. One possible scenario could be changing your web application firewall to AWS WAF with managed rules or swapping a self-run email system to an online email service SaaS offering.
Pros and Cons of Re-Purchase
Pros:
- Reduction in effort and speedy migrations
- Elimination of dependency on custom hardware and proprietary technology platform
Cons:
- Difficulty to analyse dependencies on current system
- IT Team skills need enhancement to know how to work on new cloud system